You can see the drive gears in the image above. The final gear has a small bar which flips a switch to one side or the other. The circuit does this without the need of a microcontroller. A 7400 series NAND gate chip, some passive components, and two mechanical relays are all it takes. At each push of the button, the logic chip trips one of the relays to trigger the appropriate motor direction based on the current state of that switch. You can press the button during movement, but all that will do is delay the inevitable flip of the switch.

[Dino] is staying true to his goal of hacking one project every week. This time around, he’s working on a toy that will amuse and delight his cats. The project centers around a mouse house that has two holes where mice can stick their heads out. When they do, a little LED lamp illuminates their appearance in hopes to catch the eye of your lazy kitty.

The mechanism that automates this device is quite clever and reminds us of the most useless machine. That is, the armature that holds a mouse on either end actuates a limiting switch in the middle of the box when it moves to expose one of the mice. Each of those mice is attached with a rod, along side a leaf switch that makes the mouse retreat when boinked on the head by the cat.

It only takes [Dino] about six minutes to walk us through the build in the video after the break. What follows is a walk through of the wiring and some playtime with the family pets. Despite the intended purpose, it looks like the dog is much more interested than the cat. Either way, it’s a winner in our book.

[Brett] posted about his most useless machine build. His project gives us a chance to massacre the language in the title because it uses the lowest parts count we’ve see with these machines. The logic is controlled by our friend, the 555 timer. Add to that just one servo motor, two switches, three resistors, two caps, a diode, and a battery pack and you’re in business. The hardest part to find locally is the servo but check at a hobby/RC store. If you don’t have to put in a parts order this can be your next impulse project.